ALBUQUERQUE, N.M. — The radiation exposure of at least 13 workers at a nuclear dump in a New Mexico salt bed more than 2,000 feet below the ground has brought new attention to the nation’s long struggle to find places to dispose of tons of Cold War-era waste.

The above-ground radiation release that exposed the workers during a night shift two weeks ago shut down the facility as authorities investigate the cause and attempt to determine the health effects on the employees. The mishap has also raised questions about a cornerstone of the Department of Energy’s $5-billion-a-year program for cleaning up waste scattered across the country from decades of nuclear-bomb making.

With operations at the Waste Isolation Pilot Plant on hold, so are all shipments, including the last of nearly 4,000 barrels of toxic waste that Los Alamos National Laboratory has been ordered to remove from its campus by the end of June. Other waste from labs in Idaho, Illinois and South Carolina is also without a home while operations are halted.

The dilemma about what to do with the nuclear waste is highly politicized.

The government spent an estimated $15 billion on a proposed nuclear waste dump at Nevada’s Yucca Mountain that has not been completed. The Yucca site is fiercely opposed by Nevada lawmakers, including Senate Majority Leader Harry Reid.

By contrast, New Mexico’s congressional delegation has largely supported the Waste Isolation Pilot Plant, which has been accepting waste since 1999 and employs about 650 people. The site is limited by law to plutonium waste from making weapons, but experts say salt beds at the site may be suitable for radioactive waste from commercial reactors.

Many scientists consider the unique geology of the location to be ideal for disposing of tainted materials like tools, gloves, glasses and protective suits. Over decades, with pressure from the ground above, the salt deposits settle around the containers and entomb them.

Edwin Lyman, a nuclear expert at the watchdog group Union of Concerned Scientists, said the accident could curb enthusiasm on Capitol Hill for the underground site.

“I think from a political standpoint this is going to put a damper on some of the more ambitious expansion plans,” he said. “The narrative is that facility is super-safe. Now that they’ve had a serious incident, that’s no longer valid.”

Officials said they don’t yet know what doses of radioactive material the workers absorbed, and that it’s too soon to speculate on what the health effects might be.

Tests showed traces of the element americium. Once in the body, americium tends to concentrate in the bone, liver and muscles. It can stay in the body for decades and continue to expose surrounding tissues to radiation, increasing a person’s chance of developing cancer.

On Feb. 5, the mine was shut and six workers were sent to the hospital for treatment of smoke inhalation after a truck hauling salt caught fire. Nine days later, a radiation alert activated in the area where newly arrived waste was being stored. Preliminary tests show 13 workers suffered some radiation exposure, and monitors as far as half a mile away have since detected elevated levels of plutonium and americium in the air. Ground and water samples are being analyzed.

Officials said they’re confident the incidents are unrelated. And while they emphasize that the levels detected off-site are no more harmful than a dental X-ray, they have not been able to go underground, and have not directly answered questions about how contaminated the tunnels might be.